use strict;
use warnings;

$| = 0;
print $|++ . " " for (1..4);

$| = 0;
print "\n";
print $|-- . " " for (1..4);

##</code><code>##

0 1 1 1 
0 1 0 1 

##</code><code>##

use strict;
use warnings;

my $x = 1;
print $x ^= 1 . " " for (1..4);

##</code><code>##

0101